Question on Lowrance GPS puck and SS transducer location

[marlin]

Well everything is finalized now and I'm in the long queue to get my 721. I told my dealer I'd send him a PDF at the end of the week on all the rigging details I would like to see on my boat. I was reading the Lowrance installation manual in preparation and a number of posts online and I have the following questions:

1) Since it is best to place the GPS antenna near the SS transducer has anyone tried to fit the puck on the inside of the boarding handle near the splash well? It looks like it might be too tight. Basically I'm thinking near where the remote oil fill usually sits, but on the other side of the handle to ward the middle of the boat. I'm worried if I put it in the location normally reserved for the remote oil fill that people fishing on the back deck will step on it all the time.

2) According the the Lowrance installation manual you are supposed to position the SS transducer within 1 foot of the 2D transducer to get the 2D and DI overlay to work well. Maybe I'm missing something, but this seems impossible because of the size of the steps on the back of the boat. Has anyone seen an issue with the mounting of the SS transducer on the hole shot plate and the thru-hull transducer in the bilge area? Can you mount a 2D transducer adjacent to the SS transducer on the hole shot plate and also have a 2D transducer in the bilge? Something where the HDS unit would automatically switch between the different 2D transducers depending if the boat was on plane or not?

Thanks and back to waiting.

[EdDavisKY]

SS Transducer put on the center line of the hole shot plate on the JP. Where I had mine and worked great.
The puck on my last rig I put back where you are talking about, and had not problems but if to do over again would put it behind the drivers seat....more out of the way location.
New rig going to put both my HB 1198 GPS antennas below deck to start with and see how that works.

[Todd Driscoll]

The LGC-4000 externals provide a 5X/sec update rate, less position error and less wondering/loss of direction while fishing relatively still. The internals do function very well, but like the older 2000s and 3000s, just update 1X/sec.

[idbefishing]

To have more accurate waypoints. The waypoints you marked is based on the location of the puck but the structure that you saw is 10ft behind you.

[SHOboat719]

Guys,
Maybe I am missing something here but, I need some help understanding why the thought of placing the puck over the transducer is going to give a marked improvement to pinpointing your waypoint.
First and foremost there is a error factor of +/- 6ft when using using even the highest quality reciever(LGC-4000). So, that being said you've got a 12ft diameter as to where your waypoint could be interpretted.
Secondly, I don't think most of us fish directly on our waypoint, typically 30-60ft away, right? So, your cast are an assumption you are hitting the structure or cover until you actually come in contact with it, right?
JMHO, Put the puck where it the least obtrusive, typically behind the seat. I assure you it will be within that 12ft diameter.

For those who swear by putting it over the 'ducer, if it works keep doing it!

[EdDavisKY]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by SilverFox66 &raquo;</td></tr><tr><td class="quote">My question is... why all the external antennas on the Lowrances, instead of using the internal antennas?</td></tr></table>

Barry on my last rig I started out using the internal antennas, and found it had a up to 35' -50' error margin and lost the signal quite a bit, especially running at WOT.
With the external antenna my errors dropped to a max of 15' and track was maintained in all situations. Hope that explains why some are using the external over the internal antenna without getting into the way faster updating capabilities over the two, which also accounts for the better signal as well.

[marlin]

Ed,

I was told the newer HDS units have improved the internal antenna performance (2010 models and newer). Were you using an older model?

Eric,

The argument for the antenna over the transducer is because of the ability to mark something on your SI/SS as waypoint. That mark is relative to the transducer, but it is given the coordinates of the GPS antenna. Sure the error is maybe 5 foot. In most situations, I've seen GPS antennas be accurate to around 10 foot. The 5 foot error is less than that, but it is additive. You could try to just remember which waypoints came from the SS/SI screen and which didn't to compensate for this. Also the error is relative which direction the boat was traveling when the mark was originally made.

Personally, I think they could easily eliminate this whole issue by providing the user the ability to input the offset of the puck from the SS transducer. The transducer has an orientation, so this can easily be computed. Still I have no experience with SS/SI and I'm seeking advice in general as to how much this really matters. I would figure this out on my own except for the hole in the boat required to mount it.


Modified by marlin at 5:29 AM 3/31/2011

[SHOboat719]

Understood. I guess I don't get that granular. That is probably why I don't consistently catch fish!

[falcooon]

GPS error has a lot to do with your location vs the satellites etc. I have never seen accuracy better than 12 feet on any GPS...(including my sailing experiences). Think of what we are talking about here ...12 feet... for recreational boating! ..fantastic compared to a Sextant!

I would not get too picky about this issue and put the puck and or transducer where they work the best and out of the way.

The Humminbird gps antenna's on my 721 came from the factory in the perfect location by my judgement.

Either way you will enjoy this boat and the fish in the boat will come from the line in the water!

Good Luck

[EdDavisKY]

Marlin YES I was using the older models, first yr they came out. New rig going with HB tho. Can put their GPS antennas under the deck without loosing signal strength

[EdDavisKY]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by falcooon &raquo;</td></tr><tr><td class="quote">

The Humminbird gps antenna's on my 721 came from the factory in the perfect location by my judgement.

Either way you will enjoy this boat and the fish in the boat will come from the line in the water!

Good Luck
</td></tr></table>

Could not agree more, most GPS antenna placement is personal preference anyway

[idbefishing]

So many times I've cast and cast and didn't hit what I had marked. It's pretty hard to find a single tree or small brush/rock pile in open water.

[SHOboat719]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by idbefishing &raquo;</td></tr><tr><td class="quote">So many times I've cast and cast and didn't hit what I had marked. It's pretty hard tmo find a single tree or small brush/rock pile in open ater.</td></tr></table>
My point exactly. If in a perfect world, the gps was perfectly accurate and you were fishing right on top of your waypoint, then yeah. But even then you fish at the front of the boat not the back so you are fishing 20ft from your reference anyways

[marlin]

Thanks for the feedback guys. I was told by a couple of the recognized GPS/SI gurus on this site that the antenna placement made a noticeable difference to them. I'm just a mortal user though, so I was wondering if it would for me. I am very technical and precise by nature, so I thought it might.

I have a while to ponder this while I wait in line. It's only been a week since I put my order in and it feels like a month. I feel like a kid just before Christmas morning.

I do know I used to use my little hand held GPS to often get within 5 foot of marks on land. It wasn't always that close, but I can't recall a single instance of more than 15 foot of actual error even though it would often tell me the ETE is something like 21-30 foot. I think if you are going by the GPS unit's indication of error that it is purposely being pessimistic for legal reasons. Oh well, It's something to think about.

[SHOboat719]

Marlin,
Healthy debate is awesome It makes the wait go by and increases our knowledge base. I cannot believe how much I have learned in this forum. Hopefully, I have contributed some thought provoking insight as well(I doubt it)
At the end of the day, I just want my dang BOAT!
Keep'em coming.

[falcooon]

"At the end of the day, I just want my dang BOAT!"


WELL SAID!!!

Hang in there guys .... all will be well. Enjoy the excitement as this is one of the best times of your life!

[EdDavisKY]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by idbefishing &raquo;</td></tr><tr><td class="quote">So many times I've cast and cast and didn't hit what I had marked. It's pretty hard to find a single tree or small brush/rock pile in open water.</td></tr></table>

Next time you set a way point check you margin of error and see how many satellites your unit is picking up. That will give you information on how far off your marked way point will be off.
If you have an HDS with SS, Use it to set your way point right on the tree, to do that you must being using SS. This will set the way point below water and exactly where you want it. Forgot how to do it if you do have a Lowrance HDS unit.
But ask over in the Lowrance section and they will tell you how but it is also in the Manual.

[idbefishing]

My margin of error must have been high because if I don't follow the exact track, I don't see that lone tree a lot of times. I need to work on my xducer placement because I'm not happy with my SS images.

[EdDavisKY]

Lance the more zoomed in you are on the map the more accurate your path will be.
Like looking at a small scale map compared to looking at a large detailed area map.